add a regression test

Author: pranavk

clang/test/CodeGen/X86/avx-cxx-record.cpp

@@ -0,0 +1,23 @@
+// RUN: %clang %s -c -S -emit-llvm -O2 -march=x86-64-v3 -o - | FileCheck %s
+
+using UInt64x2 = unsigned long long __attribute__((__vector_size__(16), may_alias));
+
+template<int id>
+struct XMM1 {
+    UInt64x2 x;
+};
+
+struct XMM2 : XMM1<0>, XMM1<1> {
+};
+
+// CHECK: define{{.*}} @_Z3foov({{.*}} [[ARG:%.*]]){{.*}}
+// CHECK-NEXT: entry:
+// CHECK-NEXT: store {{.*}}, ptr [[ARG]]{{.*}}
+// CHECK-NEXT: [[TMP1:%.*]] = getelementptr {{.*}}, ptr [[ARG]]{{.*}}
+// CHECK-NEXT: store {{.*}}, ptr [[TMP1]]{{.*}}
+XMM2 foo() {
+  XMM2 result;
+  ((XMM1<0>*)&result)->x = UInt64x2{1, 2};
+  ((XMM1<1>*)&result)->x = UInt64x2{3, 4};
+  return result;
+}